ABSTRACT

A brief history of seismotectonic studies in Armenia, especially after the 1988 Spitak earthquake, and new information on the active faults shed light on several key issues and areas of research in the country. Data are provided on the geometry, kinematics, and slip rates of several important active faults, including the Pambak-Sevan-Syunik fault system, and Garni, Akhouryan, Javakhq, Sizavet, and Akera faults, based on geological observations and global positioning system measurements. An updated map of active faults and a regional seismotectonic model of Armenia and adjacent countries are presented. Two cases studies are highlighted. The first concerns the question of the epicenter locations and magnitude assessments for the Dvin earthquakes of the ninth century CE. New evidence and reanalysis of earlier information indicate that serious damage of historical buildings and significant secondary soil deformations in the Garni fault zone occurred around the second part of the ninth century. This evidence questions the previous localization of the epicenters of the 863 and 893 CE events in the ancient Dvin city area. The Garni fault is located just 17 km north of Dvin, and strong earthquakes in its zone were quite capable of causing damage to that city. The second case examines active faults in the Lake Sevan basin, where pull-apart structures between the segments of the Pambak-Sevan-Syunik fault are identified on the lake floor. The length of these transtensional structures is from 11 to 15 km, and their widths vary between 5 and 7 km. Seismotectonic and geochemical activity of the faults on the lake floor gives a consistent picture. The faults in the basin and on the floor of Lake Sevan are oblique normal faults with a right-lateral strikeslip component, and they reflect an E-W extensional setting.